Computer multimeter

ABSTRACT

With added circuits and the computer&#39;s existing internal circuits and devices, a PC can function as a multimeter. For those users who are testing, designing or analyzing an electronic device, which requires the features of a computer and a multimeter, the subject invention provides convenience to the user. This subject invention will reduce or eliminate the cumbersome handling of two pieces of equipment on the same workbench.  
     The PC multimeter utilizes some of computer&#39;s existing devices, such as output devices, input devices, microprocessor and memory. The PC multimeter also comprises additional multimeter specific circuits assembled on a PCI or ISA I/O board which is mounted in the PCI or ISA expansion slot inside the computer, and only two test leads connected to the I/O board are extruding outside of the computer. The leads are connected to the device under testing. This PC multimeter includes the functions of a voltmeter, a current meter, an ohmmeter and a frequency counter. A function is initiated by a key on the keyboard, and the proper range is automatically selected by the microprocessor of the computer. The measured result is displayed on the monitor screen of the computer.

BACKGROUND OF THE INVENTION

[0001] There are many handheld multimeters, which can be interfaced with a computer. However, this arrangement uses two separate apparatus, a computer system and a voltmeter. Therefore, a user should carry a multimeter to do the test, which requires a displaying screen and an electrical measuring device. The selection of a function is controlled from the handheld multimeter and the measured results are displayed on the computer screen. The handheld apparatus should be connected to the rear side of the computer every time it is used. The multimeters interfaced with computers are using serial communication cables. The serial data communications are very slow in transferring data from one device to the other. A parallel data cable can be used, however, this will be costly and bulky.

[0002] The aforementioned facts are telling that the multimeters of the prior art are very inconvenient and inefficient to the user in comparison to the computer multimeter of this invention. All functions can be accomplished with only a handheld multimeter. However, the handheld multimeter provides very limited feasibility such as displaying just the measured value. It cannot display a meaningful message nor can it draw an eye-catching illustration.

[0003] If a versatile and multi-faceted multimeter is needed, it can be made, but the cost will be expensive. It is the recent trend that engineers, designers, and technicians are using a computer as much as possible for their work because the computer provides unlimited capabilities. The above-listed facts have raised a strong incentive to come up with a new invention of the computer multimeter. This invention is named a PC Multimeter, or Computer Multimeter. The PC Multimeter comprises combination of existing computer circuits and multimeter-specific-circuits.

FIELD OF THE INVENTION

[0004] A method for making computer multimeter by adding multimeter circuits to the existing computer resources in a computer system. In general, a computer can perform many different functions. This invention adds measuring functions to a computer system.

SUMMARY OF THE INVENTION

[0005] The PC Multimeter comprises input devices such as a keyboard, or disk drives, output devices such as a monitor screen, and internal component devices such as a microprocessor or memory. The above described devices are inherent in the computer. Said multimeter also comprises PPI, buffer/transceiver, A/D converter, timer/counter, and analog measuring circuits. This invention utilizes the existing computer circuitry and devices as part of the PC multimeter as listed above. The other part includes multimeter-specific-circuitry assembled on an I/O expansion board. The I/O board is mounted in an I/O expansion slot inside the computer. Except input/output devices, all circuits and devices are enclosed inside the computer. The only elements of the PC Multimeter extruding outside of the computer are two test leads, which connect the PC Multimeter to the device being tested. Being located inside the computer, the added multimeter-specific-circuits become part of the computer, providing expanded multimeter functions to the computer. The functions of the PC Multimeter are very versatile, and its displaying capability is unlimited, for example, a numerical value, a word message, an illustration, a table, or a graphical representation for a measured magnitude.

[0006] This invention provides the ability to have a very fine resolution by adding multiplier circuits for a very small magnitude signal. Since additional multimeter-specific-circuits are added to the existing computer circuits, the buffer and transceiver circuits are inserted between them. The circuits provide high impedance between existing computer circuits and the added circuits preventing the latter from shorting out or loading down the former circuits. The subject multimeter includes the function of a frequency counter in addition to the most common voltmeter, current meter and ohmmeter. The edge shaping circuits convert any incoming periodic signal into a rectangular wave which is easier to trigger the frequency counter. The counter counts the input frequency and couples the measured result to the microprocessor through the interfacing circuits, which includes buffer/transceiver and programmable peripheral interface circuits.

[0007] For the analog measuring circuits, a key from the keyboard initiates a function and the microprocessor controls the pertinent switch. The appropriate range is automatically selected by the microprocessor under a program control. Five function switches are utilized, one for each function. Those switches are high current and high voltage electronic switches. The range switches are typical bilateral electronic switches. Even though the computer multimeter of this invention includes only five functions, any number of functions can be added to it, because today's microprocessor equipped within a personal computer has unlimited control capability.

DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a block diagram of the computer multimeter showing each side of the I/O expansion board, and the existing circuits and device.

[0009]FIG. 2 is block diagram of the I/O expansion board showing the multimeter specific devices and a bracket which is used to mount the board in the expansion slot.

DETAILED DESCRIPTION OF THE INVENTION

[0010] The PC Multimeter of this Invention has the following Features:

[0011] 1) Capabilities of calculation, diagnosis, analysis, and displaying of the test result with computer resources such as microprocessor, memory, keyboard and monitor screen.

[0012] 2) Simple and easy operation.

[0013] 3) Program control for overload protection.

[0014] 4) Program control for automatic range changes and function selection.

[0015] 5) No manual switches (for functions or ranges).

[0016] 6) High resolution ranges with multiplier circuits.

[0017] 7) Accurate frequency measurement with timer IC.

[0018] 8) Buffering circuits for providing high impedance between computer circuits and multimeter specific circuits (I/O expansion board circuits).

[0019] 9) Accurate current measurement due to the microprocessor manipulation.

[0020] 10) Vastly different functional availability.

[0021] 11) Stylishly displaying of the measured results and messages.

[0022]FIG. 1 shows the block diagram of a PC multimeter, which comprises two sections; existing computer device (10) and I/O expansion board (1). The I/O expansion board (1) includes multimeter specific circuits, which is added to a computer to provide the additional multimeter functions to the existing typical computer functions. The analog measuring circuits (2) include range select resistors, program controlled function switches, range select switches, and high resolution multiplier circuits for current meter and voltmeter. The main functions of the analog measuring circuits are to select a function and an appropriate range for the specific value to be measured. Analog digital converter (3) receives the measured value by (2) in the form of analog voltage, converts the received voltage into a digital value representative of the input analog voltage and outputs the converted digital value to the microprocessor (11) via PPI (6) and buffer and transceiver (7). If 8 bit ADC chip is used, the range of the output digital value will be 0 to 255. If V_(REF)=5 Volts, each digital step is equivalent to approximately 20 mV (5/255), and the maximum analog input voltage is 5 volts. The range circuits at the input terminal should be designed for the input voltage not to exceed the maximum allowable voltage. Chip select signal generator (9) decodes the encoded address information coupled from the microprocessor, generates the chip select signals, and send the signal to select the requested devices. The functions of the programmable peripheral interface circuit (6) interfaces the data between microprocessor (11) and multimeter specific circuits (1). For example, the address decoder (9) receives an address information of an I/O address, either ADC, PPI, or timer/counter, then it selects the specific device, receives data from the microprocessor, and deliver the date to the device selected. PPI 8255 has 3 data ports and one control register. With three data ports, the chip has total 24 bits of data lines. Buffer and transceiver circuits (7) provides high impedance between microprocessor (11) and multimeter circuits (1). The buffer and transceiver circuits prevents the multimeter circuits from shorting out or loading down the microprocessor in case a circuit is shorted in the multimeter specific circuits side. This circuit is very important in the computer multimeter circuits by virtually isolating the two sections, the existing computer resource section and I/O expansion board section in terms of impedance. On the other hand, it couples data, address, and control signals without any loss of the signal fidelity. The two sections are communicating data in parallel; therefore all signal lines should be buffered to protect the internal computer circuits. The following description is pertaining to the existing computer circuits and devices (10). The microprocessor (11) receives a function command from input device, controls the associated circuits and devices, manipulates data acquired through the various functions in the multimeter circuits (1), and displays the manipulated results on the monitor screen. The keyboard provides specific key value for a specific function to the microprocessor. And a disk drive may input a command file or a data file to the microprocessor. The memory may store the command file and/or data in it while they are processed. Output devices may include typical computer monitor and disk drives. For this particular application, the computer monitor screen is used to display the measured value or pertinent message on it. This invention takes the advantages utilizing the existing resources in the computer system which gives the powerful means controlling the related functions and ranges, storing data or program, and displaying the measured result rather stylishly on the computer screen.

[0023] The interrupt controller can be used for an interrupt service, which is very powerful feature in a computer system. For example, an interrupt service can be applied to a frequency counter with an external timer chip. The timer can be programmed to measure frequency and the internal timer can be used to measure the time for one second. When one second time is up, it will trigger an interrupt. This will invoke a service routine, which will read the number of frequencies stored in the counter. The timer and speaker circuits (14) can be used for warning signals. For example, when applied voltage is higher than the maximum allowed voltages, it may beep with certain tones, and when an input current is higher than the maximum allowable value, it will beep with another tone. FIG. 2 shows the layout of an I/O expansion board on which the multimeter-specific-circuits are assembled. The I/O board is eventually mounted in the I/O expansion slot on the computer motherboard. It will stay in the computer under normal operation of said multimeter. The I/O expansion board can be either PCI, ISA, or any other type of interfacing architecture board to be suited for the existing I/O expansion slot. The expansion board is also called I/O adapter card. The timer circuits will receive an unknown AC signal and measures the frequency of the incoming signal. The waveshaping circuits comprises either operational amplifier circuits or emitter coupled logic circuits which shapes the incoming signal to a rectangular wave which triggers at more precise time. The timer/counter circuits should be programmed to count the frequency of an incoming periodically repetitive AC signals. 

What I claim as my invention is: 1) A computer multimeter apparatus embodied inside a computer for measuring the magnitude of electrical value under the control of existing computer resources inherent in the computer, said apparatus comprising: a) I/O expansion board means containing the multimeter-specific-circuits means for measuring and processing a measured value of a function where functions include voltage measurement, current measurement, resistance measurement, and frequency measurement; and b) the existing computer resource means for manipulating the received data, displaying the manipulated data, inputting the command for a function from a keyboard. 2) The computer multimeter of claim 1, wherein said I/O expansion board means further comprises: a) input connection means for receiving a measuring value of the device under the test: b) analog parameter measuring means, for measuring the magnitude of a selected function; c) data conversion means for converting an analog value to a digital value; d) frequency counter means for measuring the input frequency; and e) buffering means for providing high impedance and transferring data between the computer circuits (specifically microprocessor) and I/O expansion board circuits. 3) The computer multimeter of claim 1, wherein said existing computer resource means comprises: computer inherent microprocessor means for coupling necessary data to the PPI device and memory. 4) The computer multimeter of claim 1, wherein said existing computer resource means further comprises: interrupt controller means for applying interrupt service routine to initiate a specific function. 5) The computer multimeter of claim 1, wherein said existing computer resource means further comprises: computer inherent input/output means for inputting function command and displaying the test result. 6) The computer multimeter of claim 2, wherein said input connection means comprises: two test leads (or probes) of which one side is connected to the I/O expansion board inside the computer, and the other side is extruding outside of the computer as to be able to connect to a device under the test. 7) The computer multimeter of claim 2, wherein said data conversion means comprising: a successive approximation ADC converter with protection switch circuits for converting the analog value measured by analog measuring means to digital value with high resolution. 8) The computer multimeter of claim 2, wherein said data conversion means comprising: an analog value measuring mean which includes function and and autorange select circuits. 9) The computer multimeter of claim 2, wherein said frequency counter means comprising: a) rectangular waveshapping means for converting any incoming periodically repetitive AC signal into a rectangular wave which can trigger the frequency counter at a more precise time; and b) frequency counter for counting the frequencies of the incoming signal. 10) The computer multimeter of claim 2, wherein said buffering means comprising: PPI means for transferring data, address and control signal information between microprocessor and the circuits contained in the I/O expansion board. Output signals from the microprocessor are present on the signal bus a very short period of time. This PPI holds the signals long enough for the I/0 board circuits to respond. 11) The computer multimeter of claim 2, wherein said buffering means comprising: buffer/transceiver means for providing high impedance between the computer circuits (especially microprocessor) and I/O board circuits. This prevents I/O board circuits from shorting out or loading down the computer circuits. 12) The computer multimeter of claim 2, wherein said buffering means comprising: chip select signal generator means for generating a chip select signal which selects a specific I/O device where I/O device includes ADC, timer, PPI, and analog measuring circuits. 13) The computer multimeter of claim 3, wherein said computer inherent input/output means comprising: a) computer inherent input means for communicating data between the user and the computer system for the operations of the various multimeter functions; b) computer inherent output devices means for displaying the measured value and the desired messages if necessary; and c) disk drives for saving programs and data. 14) A method for upgrading a computer system to include multimeter function, said method comprising: a) assembling the multimeter specific circuits on an I/O expansion board and installing the I/O board in an expansion slot inside the computer; b) installing all multimeter circuits inside the cover case except two test leads; and c) extruding only two test leads outside of the computer. 15) A method according to claim 14, utilizing existing computer resources; microprocessor, keyboard, monitor screen, memory, interrupt controller, timer, and speaker, as part of a computer multimeter. 